Diffusion v absorption

spiritofmusic

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Jun 13, 2013
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Phil, can I thank you so much for yr input, esp on PM. I'm gonna seriously consider yr suggestion of Echopanel slats on my 30° descending eaves parallel to my existing structural steels, and continuing vertically down my side walls, in the zones of first and second reflection points. It's mild absorbative qualities, and critically, ability to break up direct reflections from eaves, could be inspired.
 

Zero000

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Jul 28, 2014
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Are these ALR screens newish on the market

Phil

I don't actually know when them came on the market as I only really just started looking at it. Spent hours watching YT videos on the subject.

They are designed for ultra short throw projectors. They make viewing possible with a fair amount of ambient light in the room. But forget it in bright sunlight in a room with lots of windows. That said my OLED is rubbish in a bright room too.

I will say I find watching the 100 inch projector versus the 55 inch OLED to be massively superior as a viewing experience. You have to see the two in the flesh to realise it.

Projectors have definitely arrived.
 

Duke LeJeune

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Jul 22, 2013
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[QUOTE="pjwd, post: 649451, member: 7003"The bass traps and general absorption controlled reverberation time and the reflection/ baffles reduced early reflections smearing the sound. But there was still enough reflections going on to provide a nice reverberant tail ( not overdamped )... [/QUOTE]

Imo this is an excellent overview of what works well. Rewording it a bit:

1. Reduce early reflections because they are the ones which are most likely to smear the sound... BUT absorbing them may not be the best approach! In the studio photo, we can see that the acoustician used angled panels on the side walls to REFLECT the first sidewall reflections such that they would miss the engineer's listening position. This preserves their energy to come back as beneficial later reflections.

2. Control the reverberation times so that they are approximately the same up and down the spectrum. This is important because the ear perceives sounds which longer (which includes decaying more slowly) to be LOUDER than other sounds of equal SPL which fade away faster. But reverberation times (RT60's) alone DO NOT tell use enough information about what is going on in the room because they tell us nothing about the early reflections, nor do they tell us about the uniformity of the decay rate across the spectrum.

3. We want enough there to be "still enough reflections going on to provide a nice reverberant tail" ... which implies that we do not want to use too much absorption in the room. Remember that absorption has its effect EVERY TIME a sound wave hits it - so absorption positioned to target the first reflections is still absorbing every time a subsequent reflection hits it. And we'd like for those later reflections to have approximately the same spectral balance as the direct sound (the highs will inevitably be attenuated somewhat simply from travelling through more air), which CAN mean that the acoustician needs to address excess off-axis energy which the loudspeaker may be generating at some frequencies. The knowledge of which materials and/or treatments to use for targeting specific frequency regions is way above my pay grade.
 
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pjwd

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Jun 22, 2015
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The knowledge of which materials and/or treatments to use for targeting specific frequency regions is way above my pay grade.
Duke - not only yours :) - it is almost impossible to predict what a various panel wall types fixed to studs will absorb and reflect as they are not a proprietary tested system so its a good strategy to have some flexibility in a design so you can remove or add treatments especially in broadband and bass absorption - in my experience you usually are removing them.
Totally agree with what you said above + your other posts I have read

I have it explained to me why even the RT60 method of analysing reverb time is not that useful ... but that was too long ago
cheers
Phil
 
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Cellcbern

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Jul 30, 2015
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There is a third option beyond absorption & diffusion panels. I have done direct comparison testing between a combination of RPG BAD and Gik absoption panels, and the ZR Acoustics panels and found the latter to be significantly better even with less than the recommended sf of wall coverage. Keeping the RPG BAD panels for the side and rear walls, and ceiling (at least for now), but the ZR Acoustics panels behind the speakers are a dramatic iprovement. See my posts on the subject. ZR Acoustics panels.jpg
 
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